MacBook Pro - Help: Connecting audio to TV from MacBook Pro

I am having trouble getting audio when connected to my newish Toshiba TV. I can get picture fine but no sound. Have had no luck with this RCA Y cable:

http://www.radioshack.com/product/in...entPage=search
Plugged it into my headphone plug and then to Left and Right sockets on the TV. Then changed audio input to PC on my TV settings and went to System Preferences/Sound/Output on my Mac but doesn't seem to register that I have connected my TV as an external sound device.

Does anyone know what I am doing wrong? Would greatly appreciate any help!

The setting problem is most likely in your TV. There is no reason why that cable shouldn't work. The mac will not detect an external audio device as "conected" to the output jack. The output jack will litterally send audio signals to your TV.

The one thing I would suggest you check is Core Audio and make sure that it hasn't been switched to Digital/Optical. Make sure it is on analouge audio.

Beyond that, the only problem can be with the input settings on your TV.